Radio controlled navigational



Dec. A12, 1944. J. DUGAN RADIO CONTROLLED NAVIGATIONAL SYSTEM Filed sept. 18, 1941 5 Sheets-Shet l Dec. 12, 1944. .1. DUGAN 2,364,625

RADIO CONTROLLED NAVIGATIONAL SYSTEM Filed Sept. 18, 1941 5 Sheets-Sheet 2 um Fi 5 la Das. l2, 1944. J. DUGAN 42,364,625

RADIO CONTROLLED NAVIGATIONAL SYSTEM Filed Sept. 18, 1941 5 Sheets-Sheet 3 jig. Z

Dec. 12, 1944. J, DUGAN 2,364,625

RADIO CONTROLLED NAVIGATIONAL SYSTEM Filed Sept. 18. 1941 5 Sheets-Sheet 4 SR2-nonfarm fave/#0f Dec.` 12, 1944. J,Y DUGAN Y 2,364,625

RADIO CONTROLLED NAVIGATIONAL SYSTEM Filed Sept. 18, 1941 5 Sheets-Sheet 5 Patented Dec. 12, 1944 RADIO CONTROLLED NAVIGATIONAL SYSTEM Joseph Dugan, Los Anfles,

one-half to Evelyn Calif Calif., assig'nor of Dugan, Los Angel.

Application September 18, 1941, Serial No. 411,408

' (ci. 25o-2) 19 Claims.

This'invention is an improvement in the Di.

rection and position indicating system disclosed in my United States Patent No. 1,959,264, May

15, 1934; and, this application is a continuationin-part of my application Serial No. 361,639 for Radio controlled steering system, filed October 17, 1940. The subject matter common to these two applications includes mechanism on a mobile craft, automatically controlled by energy derived from two spaced apart radio transmitting stations, for steering such craft automatically on to, and in drift-corrected movement in a predetermined direction along, .a straight course passing through said stations. It also includes means controlled by energy derived from a third radio transmitting station,'at one side of said course, for continuously indicating the position of the craft on that course.

In its broadest aspect, this invention relates to a system in which direction determining devices (telescopes, directional radio antennae, directional gyroscopes and the like) are mounted on a mobile craft to rotate independently about normally vertical axes and are operably connected either to indicating mechanism to enable a pilot to steer the craft manually, or to mechanism for steering the craft automatically, on to and in drift-corrected movement in a predetermined direction along, a straight course passing either through two spaced apart objects (radio transmitters, light beacons etc.) upon' which two of said devices are separately held trained, or along any predetermined compass course through any of said objects. f

The main object of the present invention is to simplify the craft-steering operations of the systems disclosed in my said patent and pending application, by the substitution of a pilot director having a single steering pointer reading against a single lubber-line for the dual pointer steering indicator disclosed in said patent and pending application.

Another 'object of this invention is to provide apparatus oi this type with means adjustable, alternativen/to arrange the steering mechanism of the craft for manual or automatic control without interfering with the operation oi the single-pointer steering indicator.

A further object of this invention is to provide apparatus of this type` with means for continuouslyindicating the ground speed. angle of drift and position of the'craft on said course, as well as the distances traversed between any selected` Points thereon.

Other objects of the invention will become sip-f,

parent as the detailed description thereof proceeds.

In the drawings:

Fig. 1 is a diagrammatic layout, in elevation,

of the apparatus used for steering mobile craft on to andV in drift-corrected movement in a predetermined direction along s. straight course passing through two spaced apart radio transmitters,

and for operating mechanism to indicate the P0- sition of the craft on that course and its ground speed; A

Fig. 2 is a diagrammatic layout, in plan, of the apparatus shown in Fis; 1;

Fig. 3 is a fragmentary diagram illustrating the mechanism for adjusting the steering apparatus, alternatively, for either manual or automatic control; Y

Figs. 4, 5 and 6 are diagram used to explain the underlying principle involved in the operation of the steering mechanism disclosed in Figs. 1, 2 and 3;

Fig. '7 is a vertical section taken on the line l-'i of Fis. 8; l

Fig. 8 is a fragmentary plan of ground speed and lposition indicating mechanism connected for operation by the apparatus shown in -Figs. 1 and 2;

' Fig. 9 is a diagram illustrating the principle involved in the operation of the ground speed and position indicating mechanism shown in Fig. 8:

Fig. 10 is a wiring diagram;

Fig. 11 is a diagram illustrating, by comparison, the operation of the single and dual-pointer indicators;

' Fig. 12 is a fragmentary layout illustrating the use of sighting devices as substitutes ior the dlr'ectional radio antennae of Figs. 1 and 2;

Fig. 13 is a diagrammatic layout illustrating a system in which'a directional gyroscope replaces one of the radio compasses of the @stem shown in Figs. 1 and 2; and

Fig. 14 is-an explanatory diagram.

For proper understanding oi' the principles/lnvolved in the steering of mobile craft in accordance with this invention, from any location within range of the course-dening objects, on to and in drift-corrected movement in a predetermined direction along a straight course passing through two of such objects. it will be necessary to consider the space on opposite sides of said course as divided into `three zones by planes perpendicular to said course at the course-defining objects. In the intermediate zone, the craft moves between the two course-defining objects. In one of the outer zones, the craft moves toward both objects; and, in the other outer zone, the craft is considered as moving away from both objects.

With this division into zones understood, the principle involved, and as illustrated in Figs. 4, and 6, requires: (1) that when the craft is in drift-corrected movement along the desired straight-line course, the rudder of. the craft must be zero-centered (alined with the fore-and-aft axis) (2) that regardless of the headings of the craft, when it is located in either of the outer zones and is laterally displaced to the right of said course (looking along the course in the desired direction of movement), the rudder must be continuously adjusted clockwise from zerocenter. through angles proportional to the continuously varying dierences between the exterior and interior-opposite angles at the fixed base of the triangles formed by drawing straight lines to the laterally displaced craft from the two spaced apart coursefdeining objects; (3) that,

regardless of the headings of the craft, when it is located in the intermediate zone and is laterally displaced to the right of said course, the rudder must be adjusted continuously clockwise through angles proportional to the continuously varying sums of the interior angles at the xed base of the triangle formed by drawing straight lines from the spaced apart course-defining ob jects to the laterally displaced craft.

The same principle is involved in the contin- Y uously varying adiustments of the rudder when the craft is located to the left of the desired course; except that in this event, the rudder must be achusted counter-clockwise, instead of clockwire, from zero-center.

The matter of determining or indicating the position of the craft during its movements along a straight course passing through two spaced apart course-defining objects is suggested in my aforesaid U. S. Patent 1,959,264 and involves the idea of continuously orienting a base plate or dial to maintain a reference line on that dial continuously alined withsaid course. With a dial so oriented, the continuous determination and indication of the position of the craft on said course may be carried out by setting up on said dial a representation in miniature of the rangles formed with said reference line by a astuces radio compassesdesignated generally by the reference numerals I and 2. 'I'hese automatic compasses are now well knownandj-have been in common use'for several years on the airlines of the United States. They are shown and -de scribed in detail on pages 250 to 257, inclusive, andv pages 305-306 of Aircraft Radio and Electrical Equipment, by Howard K; Morgan, published in 1939 by Pitman Publishing Company of New York; and, are also fully disclosed in my aforesaid U. S. Patent 1,959,264;' in the German patent to Dieckmann No. 555,826-1932; and British Patents Nos. 523,093 and 523,953 accepted July 14 and 26, 1940, respectively, and based on the corresponding U. S. patent to Moseley 2,257,- 757 October 7, 1941.

As shown in Figs. 1 and 2, the compass I includes: the receiver R-l, tunable to the frequenoy of either transmitter A or B; a loop antenna 3 mounted on a shaft 4 for rotation about a normally vertical axis; and a sense antenna 5 connected to the receiver R-I through the switch 6. The output of the receiver R-I operates the follow-up motor M-I to effect rotation of the grooved pulley 1 fixed to the lower end of the motor shaft 8. A cable 9 transmits the rotation of the pulley 1 to a similar pulley I0 fixed to the lower end of the loop-supporting shaft Il, and thereby maintains the loop A3 with its plane constantly perpendicular to a straight line joining the transmitter A to the receiver R-I. A gear I I, fixed to the other end of shaft*l 8, meshes with a. similar gear I2 mounted to rotate on a sleeve I3 extending upwardly from a gear I4, which, in turn, is mounted to rotate on a shaft I5 rotatable on a bearing frame I6.

'I'he shaft I5 is rotated by means of a gear I1 in mesh with a gear I8 fixed to the upper end ofthe rotor shaft I8 of the motor M-2 which is operably controlled by the output of the receiver R-2 of the automatic radio compass 2. The receiver R2, tunable to the frequency of the transmitter B, includes the loop antenna l2li mounted on the shaft 2l for rotation about a normally vertical axis, a sense antenna 22 being connected to the receiver ift-2 through the switch 23. Rotation of the loop-supporting shaft 2|` is effected through the crossed cable 2t connecting the straight line drawn from the craft, as it proceeds i on its course, to a. third object located on either side of the course, and by causing an arm or indicator to rotate through the same angles over this miniature representation and indicate, ou

asuitably calibrated scale, the position of the craft on its said course.

This method of determining and indicating the position of the craft on a dial which changes its position with every change in the angle of drift, is fully described in my aforesaid co-pendlng application. In this case, this objection to indicating movements on a continuously' moving (oriented) dial is eliminated by compensating for the angles of drift of the craft, and transmitting to fixed position and ground speed measuring devices nothing but the angles which the rotatand 6.) v The steering mechanism mounted on the craft includes two automatic (self-orienting) the sleeve I3. The shaft vI5 extends through this sleeve and has a pointer 32 iixed to its upper endfor alinement with the' pointer or indicator line 28 when thecraft lies on the course L. The dial 21v with its indicator 28 and the cooperating indicator 82 constitutes a pilot director which enables the pilot to determine the location of the craft relative to the desired course.

To adapt this apparatus for automatic steering, the lower ends of the motor shafts 8 and I8 have the bevel gears 33 and 34 xed respectively thereto and in mesh with the adjacent differential gears 35 and 38 which are rotatably mounted on the shaft 31. These gears 88 and 86 mesh with the bevel gears 31 and 38 on the opposite ends of the differential spider 88 pinned to the shaft 31 to complete the differential gear set. A sleeve 31" is splined on the shaft 31' to slide thereon and rotate therewith. Bevel gears 38" and 33", secured to this sleeve 31", are arranged for movement alternatively into or out of mesh with one side or the other of the bevel gear 40.

The sleeve 31" may be locked by lever mechanism, hereinafter described, in an intermediate position, with the gears 38" and 38" clear of the gear 40, to permit manual control of the rudder mechanism when desired. The sleeve 31" has a circumferential groove 4I formed therein to receive thepins 42 extending radially inward from the opposite arms 43 of a yoke formed on one end of a clutch-throw lever 44. (Shown diagrammatically in Fig. 3.) The gear 40 is fixed to the upper end of a shaftV 45 to which is ilxe'd the pulley 48 operably connected to the rudder 41 by the cable 48.y y

The direction of movement of the clutch sleeve 31" to cause one or the other of the gears 38 or 38 tomesh with the gear 48 dependsupon the location of the transmitters A and B relative to the craft as it proceeds in one direction or the other on the course passing through said transmitters. 'I'he reasons for this dependance and the necessity for using the dlierential gearing will appear fromconsideration of the diagrams shown in Figs. 4, 5 and 6. In these diagrams, the craft is indicated by the reference characterV; the solid circle at the bow of the craft represents the gearvII of the motor M-I; the solid center circle represents the dial 21 which is fixed to the gear I2 in mesh with gear I I; the smaller broken circle `at the center represents the gear I1 xed to the shaft I5 having the pointer 32 secured to its upper end for rotation over the dial 21; and, the smaller circle at the stern represents the gear I3 fixed -to the rotor shaft I8 of the motor M2 to effect rotation of the pointer 32 through the gear I1 and shaft I5.

Fig. 4 illustrates the craft V as starting in movement toward the transmitter B from a starting point S along a straight course L passing through the transmitters B and A, As initially installed on the craft, the apparatus will be mounted with the indicator or reference line 28 and the pointer 32 in alinement with each other and with the fore and aft axis of the craft, or with a. lubber-line representing that axis. At the starting point S, the craft is headed along the course L under alr- ,speed PW, and is subjected to a side wind WE which will cause the craft to crab or drift at ground speed PE eventually to the position P-I.

unless this heading be changed in the meantime to correct for this drift. In position P-I, the craft lies to the right of the course L and is headed along the line L-I parallel to the course L; consequently, the rudder 41 must be moved to the left (clockwise) in order to steer the craft toward the desired course L.

If in this position P-I of the craft. the receivers R-I and BP2 are tuned to the frequencies of the transmitters A and B, respectively, the gear II will be rotated clockwise by the motor M-I through the angle APA to impart a counterclockwise rotation through the same angle APA to the dial 21 and its indicator reference line 28 which is represented in Figs. 4, 5 and 6 by the line PA. Similarly, the gear I8 will be rotated clockwise .by the motor M-2 through the angle A'PB to impart a counter-clockwise rotation through the same angle APB to the pointer 32 which is represented in Figs. 4, 5 and 6 bythe line PB.

Clockwise rotation of the!- gear I8 is obviously 16 accompanied by clockwise rotation of the bevel .gears 34 and 33 through the angle A'PB; while clockwise rotation of the gear II and its connected gear 33 causes counter-clockwise rotation of the differential gear 35 through the smaller angle APA. Obviously, the result is a clockwise rotation ofthe diierential spider 39 and the shaft 31' through the angle A'PB minus the angle APA; that is, a clockwise rotation or the shaft 31" through the angle APB which is clearly equal to the dierence between the exterior and in-.

terior-opposite angles at the base BA oi the triangle formed ,by drawing straight lines from the transmitters A and B to the craft V in its later-v ally displaced position P-I.v Since the rudder 41 must be rotated clockwise to steer the craft toward the line L, it is apparent that the sleeve 38 must be moved to cause engagement of the gears 33 and 40.

It is obvious that drift of the craft V to the left of the course L, instead of to the right, will call for opposite rotations of the receiver loops, the gears II and I8 of the reversible motors M-I and M-2, and rudder 41. Therefore, the gears l 38 and 48 must remain in mesh while the craft is in movement toward the transmitters A and B on either side of the course L.

In order to steer the craft from the position P-I on to the line L and in drift-corrected movement along that line in the direction BA, the rudder 41 must be rotated clockwise through an angle proportional to the angle APB. Then, when the craft moves toward the line L, the angle APB becomes smaller and smallerand the rudder angle decreases proportionally; untill finally, the angle APB vanishes, the lines AP and BP coincide; and the craft "crabs along the course L, headed into the wind WE at the drift angle WPE under airspeed PW and ground-speed PE, with the rudder 41 allned with the fore-and-aft axis. The correction for drift is thus completely automatic. and the track of the craft eventually approaches the desired drift-corrected course L through the transmitters A and B asymptotically.

In Fig. 5, the craft V is shown as starting from the transmitter B toward the transmitter A under a cross wind WE and at air-speed PW, or headed along the course L. If` this heading be maintained, the craft will eventually arrive at the p0- sition P-2 with its fore-and-aft axis lying in the line L'2 parallel to the course line L. With the craft in position P-2, it is evident that the motor M-I must have rotated the gear II clockwise through the'angle PPA to cause counter-clockwise rotation of the dial 21 and its indicator reference line 23 through the same angle BPA. It is also evident that the motor M-2 must have rotated the gear I8 counter-clockwise through the angle B"PB to cause clockwise rotation of the pointer 32 through the same angle B"PB. This means that the dial 21 and pointer 32 rotate in.,

opposite directions when the craft V is laterally displaced from the course L during itsl ilightbef tween the transmitters A and B.

Counter-clockwise rotation of the motor M-2 and its associated -bevel gear 34 causes counterclockwise rotation of the dierential gear 38 and spider 38; and, clockwise'rotation ofthe motor M-I and its associated gear 33 causes counterclockwise rotation of the diiierential gear 38 and spider 38. This means that the angles BPA and B"PB are added in the differential tc rotate the shaft 31' counter-clockwise through the sum of theangles BPA and B"PB; or, the angle B"PB which is obviously equal to the sum of the interior annee at the base BA of the triangle formed by drawing straight lines from the transmitters A and B to the craft in its laterally displaced position P-2. The necessary clockwise adjustment of the rudder 41 through an angle proportional to the angle B"PB requires a shift of the sleeve 37 to mesh the gears 38 and 49, as shown in Fig. 1.

In Fig. 6, the craft is -shown as headed for movement along-the course L away from both' transmitters A and B. I f this heading be maintained, the craft will eventually arrive at the position P-3 headed along the line L-3 parallel to the course L. If the receivers R-I and R-Z be now tuned to the frequencies of the transmitters A and B, respectively, the dial'21, with its reference line 23, and the pointer 32 will rotate through the angles CIPAY and C'PB, respectively; The necessary counter-clockwise rotation of the motor M-l and its associated gear 33 causes a clockwise rotation of the 'differential gear 35 and spider 39 through the angle CPA; while the counterclockwise rotation of the motor M-2 and its associated gear 34 causes counter-clockwise rotation of the differential gear 35 and spider 39 through the smaller angle C'PB. The result is a clockwise rotation of the shaft 3l through the angle C'PA minus the angle CPB; or, the angle BPA, which is lclearly equal to the difference between the exterior and interior-opposite angles at the base BA of the triangle formed by drawing straight lines from the transmitters A and B to thecraftin its laterally displaced position P-3. In this case, since the shaft 32 rotates clockwise, it will be necessary to shift sleeve 3l' to mesh gear 39 with gear 40 to effect clockwise adjustment of the rudder 41 through an angle proportional to the angle BPA.

It will be apparent from inspection of Figs. 4, 5

or out of mesh with the gear 52 which is ilxed to the lower end of a shaft 53 having the steering dial 54 secured to `its upper end. This dial 54 is provided with a single pointer orindicator 55 arranged for alinement with the xedLubber- Line 56 only when the craft is located on the course L.

From inspection of Fig. 1, it will be obvious that the dial 54 rotates in adirection opposite to that of the rudder 47 and through angles propoi-tional to the angles of rotation of the shaft 3l. It is obvious, therefore, that; the dial 54with its single pointer`55, cooperating with the xed lubber line on a fixed part 5l of the craft, may be used instead of lthe two Yrelatively rotatable indicators 28 and 32 to steer the craft on to and in drift-corrected movement in a predetermined direction along the course L defined by the transmitters A and B.

The gears 5|! and 52, like the gears 3B and 40, are 'shown in Fig. l in positions required for operation in the intermediate'zone--between sta- 1 tions A- and B. When in operation in either 0f linked together as shown in Fig. 3.

and 6, that the angles formed by the straight lines drawn from the transmitters A and B to the laterally displaced craft, are independent of thel headings of the craft. This means that, regardless of the headings of the craft in any of its laterally displaced positions, the automatic pilot will steer the craft from any such position (within range of the transmitters) on to and in drift-corrected movement in a predetermined direction' along the course L. For example, if the craft in position P-l were headed in a direction opposite to that shown in Fig. 4, the adjustment of the rudder 4l would still be clockwise and proportional to the angle APB, and would rst cause the the direction BA If the receivers R-I and Rf-Zv are tuned to the frequencies of the transmitters B and A, respectively, the craft will move in the direction AB. AThe rule is that the direction of movement of the craft along the course L is that direction in which the transmitter to which the receiver R-l is tuned lies ahead of the transmiti ter to which the receiver Rf-2 is tuned.

To render manual control of the craft easier' for the pilot, the apparatus includes a second sleeve 49 splined on the shaft 31' to slide thereon and rotate therewith. Gears 50 and 5l are fixed to the sleeve 49 for movement alternatively into To avoid confusion in -the drawings, the yoke arms 43 at one end of the lever 44 are omitted in Fig. 3 and the yoke end of this lever is illustrated as terminating in the axis of one of the pins 42. The' lever 44 is mounted to rock about the xed pivot 58 into the three different positions indicated by the letters I, F and O. In position I of the lever 44, the gears 38 and. 40 are meshed for operation in the inner zone (between transmitters A and B); and, in position O, the gears 39 and 40 are meshed for operation in either of the outer zones. In position F, the gear 40 is free'of both gears 38 and 39; and, the craft is conditioned for manual control.

The slide 49 is provided with a circumferential grooveV 59 to receive the pins 50 which extend radially inward from the yoke arms 5l formed at one end of the clutch throw lever 52. (See Fig. 3.) The lever 32 is mounted to rock about a pivot 53 fixed at the same distancel from the shaft 3l" as the pivot 58. The yoke arms 5l are also omitted in Fig. 3, and the lever 62 is illustrated as ending in the axis of one of the pins 6G.

A link 64, substantially parallel to the shaft 3l', is pivoted at one end to the outer arm of lever 44 and is shaped at its other end to form a lostmotion slot B5 which slidably receives a pin 66 extending laterally from the lever G2. When the steering mechanism is set for automatic operation in the intermediate zone, the levers 44 and y 62 are substantially parallel as shown in Fig. 3,

with the gears 38 and '59 in mesh with gears 40 and 52, respectively.

When the lever 44 is in the full-line position sli-own in Fig. 3, with the gears 38 and 40 meshed, the outer end 61 of the slot 65 contacts with the pin 66 and holds the lever 62 in position to keep gears 50 and 52 in mesh. When the lever 44 is thrown to position F the gear 4l) isclear of both gears 38 and 39, with the rudder free for manual control. The slot 65 is of such length that the inner end 68 thereof merely moves into contact with the pin 66 when the lever 44 is thrown from position I to position F. This means that while the rudder is free for manual control, the steermust be in either the I or O lever 44 is inthe F (free) position; and the pilot ing dial 84 is still connected for operation in the intermediate zone.

A further throw of the lever 44 from position F to position O will not only shift the gear 39 into mesh with the gear 48, but will also throw the lever 82 from position I to position O and thereby shift the slide 48to mesh the gear 8|, instead of gear 88, with the dial-operating gear 52. With both levers 44 and 82 in the O position, the steering and indicating mechanism is obviously set for operation in either of the outer zones.

From inspection of Fig. 3, it will be apparent that when the lever 44 is in the I (inner zone) position, the `lever 82 must also be in the I position; and, that when the lever 44 is in the O posi tion, the lever 82 must also be in this O (outer zone) position. It is obvious that the lever 62 position when the may throw the lever 82 into either position as required for operation in the particular zone in which the craft may be located. Any suitable means may be used for locking the levers 44 and 62 releasably in their various adjusted positions.

For determination of the ground speed and position of the craft V on the course L, a third radio transmitter S-l at one side of th craft is required to control the operation of a third automatic radio compass arrangedson the vcraft to cooperate with compasses I and 2. A possible relative arrangement of the three automatic radio compasses is shown in Figs. 1 and 2; and a possible arrangement of a third radio transmitter relative to the course L is shown in Fig. 9.

In Fig. 2, the rectangle R-3 and connected circle M-3 form parts of a complete self-orienting radio compass 88 similar in every respect to the compasses i and 2 shown on opposite sides of the shaft I8 in Fig. l. The motor M-3 is used to rotate a third loop 18 on the loop-supporting shaft 18' Iby means of the grooved pulleys" and 12 and connecting cable 13. A gear 14 xed t0 the upper end of the shaft 15 of motor `M-8 meshes with the gear i4 (see Fig. 1) toimpart rotation to the sleeve I8 which constitutes the rotor shaft of the transmitter T, the stator of which is fixed to the dial 21. 'I'he receiver R-3 is tuned to the frequency of the third transmitter S-i to cause the pointer 18, xed to the upper end of sleeve I3. to point continuously in a direction representing the direction of the transmitter from the craft. The diametral line 28 is con-l tinued over the upper face of the transmitter T which then serves as a dial 11 having a scale 18 formed thereon to indicate, with'the pointer 18, the position of the craft V as it proceeds along the course L represented by the line 28.

From inspection oi Fig. 8 it is evident that as the craft moves along the course L through the points E, F, G and H. 'the pointer 18 and the line joining the transmitter S-I to the axis of the shaft ii appear to rotate clockwise over the dial 11. Therefore, in marking the graduations 18 on the dial 11 to represent the locations of the points E,F,GandHonthecourseL,itwillbeneoes sary to arrange them so that lines Joining them tothe center of the dial 11 are at the same angles to the reference line 28 as the corresponding lines S-IE, S-IF, S-IG. and S-iH occupy relative to the line L. In other words, the graduations of the scale 18 are arranged on the dial 11 tofreproduce in miniature the conditions in space represented in Fig. 9. y

The position and ground speed indicating appa,-

accesso Iso ratus illustrated in Fig. 8 is intended to be xed to the craft V. To derive correct indications of ground speed and position on this fixed apparatus from 'the' continuously moving radio controlled members of the apparatus shown in Figs. l and 2, only the movements of the pointer 18 relative to the reference line 28 are transmitted to the repeater R-4. (See Fig. 7.)

The rotor shaft I8 of the repeater R-4, rotating in synchronism with the rotor shaft of the transmitter T, 'rotates the conducting arm 88 with its trolley 8| on to one or the other of the conducting segments 82 and 83, separated by the usual central insulating strip 84. (See Fig. 10.) The plates 82 and 83 are arranged on and insulated from the gear 84 Ywhich rotates on shaft 19 and meshes with a similar gear 85 xed to the shaft 88 of the 'servo-motor S-4 operable in one direction or the other by the movements of the arm 88 over the plates 82 or 83.

A `shaft; 81, rotated by means of the gear 88 in mesh with gear 88, extends through the fixed scale plate 89 which is provided with an indicator reference line 28 and a position scale 18' similar to the scale 18 on the dial 11. An arm 88, fixed to the upper end of shaft 81. rotates over the scale 18 to reproduce the movements of the pointer 16 over the position scale 18, and is provided with a slot 9| to receive a pin 92 extending from a nut 83 mounted on the screw 84.

The screw 94 is mounted to rotate in supporting slides 95 and 86 `to adapt the screw 94 for adjustment toward and from the axis of the shaft 81 to positions corresponding to the perpendicular distance D of the transmitter S-I from the course L.l A clamping screw 91 may be used to lock the screw 84 in adjusted position between the fixed supports 88 and 89. It will be apparent vfrom inspection of Figs. 8 and 9, that the apparatus shown in Fig. 8 is intended to represent, in miniature, the conditions in spe indicated in Fig. 9.

The-effective length of the screw 84 is a measure of thedistance traversed by the craft, and the speed of angular rotation of the screw is a measure of the ground speed ofl the craft on the course L. V'I'he amount of rotation of the screw 84 is a measure of thedistance traversed by the craft V on the course Land is indicated by the odometer |88 to which the screw is shown as connected by the gearing |8|. An over-running clutch |82 and y-wheel |83 are interposed between the gearing |8| and the speedometer |84 to produce a substantially steady rotation of the speedometer operating shaft.

-The arm 88 is provided with an index |81 reading on the position scale 1 8', and a pointer |88 extends in the opposite direction to read on the oppositely graduated position scale 18" when *so .the craft moves on the course L in the opposite l direction (H to E) and uses the same laterally located transmitting station S-l. Obviously, the odometer |88 may be set to indicate the trip mileage or distance traversed between any selected `points on the course L. The angle of drift is eliminated as a source of error, and the apparatus shown in Fig. 10 therefore gives substantially correct ground speed at any point of the course or 18'.

In Fig. 12, the system is shown as employing sighting devices as direction determining devices instead of the directional antennae of Figs. 1 and 2. In Fig. 12, the telescope 3 is shown as mounted torotate about the normally vertical axis Vof L indicated on'the position scale 18 the shaft 4". A 4grooved pulley |0 is fixed to the shaft 4' and is connected by the cable |05 .to a similar grooved pulley |06 xed to the shaft of a follow-up contact unit III! controlling the operation of the follow-up motor M|. Similarly,

the telescope 20 is mounted to rotate about the normally vertical axis of the shaft 2|', and a grooved pulley 26', fixedto the shaft-2|', is connected by a cable |09 fixed to a similar grooved pulley H on the shaft of another follow-up contact unit H2 controlling the operation of the motor M2.

'The follow-up contact units |08 and ||2 similar to that shown in Figs. '1 and 10 and require no further description since -units of this type and their mode of operation are well known in this art. The steering and indicator mecha-- nisms controlled by operationof the motors M-I and M-Z are the same as illustrated in Figs. l and 2, and the corresponding elements have been given the same reference characters. In both forms of this invention, the operation of the steering and indicating mechanisms is effected by holding the direction determining devices (antennae or telescopes) trained on the objects used to define the course of the craft or to assist in determining the position, drift and ground speed of the craft along that course. This matter is shown and described briefly in this application to emphasize the fact that the invention is not limited to the use of directional radio antennae, and to form a. basis for the use of the broad expression direction determining devices in the claims appended hereto.

In the system as illustrated in Figs. 13 and 14, a directional gyroscope H3 kis substituted Vfor the radio compass '2 of the apparatus shown in Figs. 1 and 2. The object of this form of the invention is` to steer the craft in drift-corrected movementin a predetermined direction along any desired compass course through a single radio transmitter. In this apparatus, the self-orienting radio compass is retained in its entirety, with the shaft 31 and the clutch controlled steering and indicating mechanisms connected operably thereto as shown in Figs. 1, Zand 3. As

-is well known in this art, the directional gyro must be` periodically compared with a magnetic compass and reset whenever found necessary. 'I'he caging and setting mechanism is also well known, and is therefore not illustrated or described herein. v

As shown in Fig. 13, the pivot shaft I I4 extends radially from the vertical ring |I5 and through the bearing H6 for the'gear vl2 and dial 21. .A direction indicating pointer ||1 is fixedto the upper end of the shaft H4 and extends in opposite directions over the dial 21. The lower pivot shaft H8 is supported in a step bearing on a. dial ||9 and has a conducting arm |20 provided with a trolley |2| vrolling over Vconducting segmental plates (not shown)` similar to those shown in Fig. 10 and similarly arranged with their 'adjacent ends separated by the -usual central strip of insulation.

'Ihe dial H9 is secured to the shaft |22 of the follow-up motor S-B, and its segmental plates are connected to this motor's field windings as indicated in Fig. 10. The motor S-I' has a transmitter T-5 fixed thereto with the shaft |22 forming a common rotor shaft for both motor and transmitter. The motor S-li and transmitte! T-5 are rotated bodily about the axis of their common rotor shaft |22 by means of the ring gear I2' and the gear fixed to an extension H3, the angle transmitted to the repeater R-5 is 8' of the radio compass shaft l. Obviously, the motor S-i and transmitter T-E rotate in synchronism with antenna 3 and the dial 21.

Ihe gyro I I3 prevents the shaft |22 from rota'- tion withthe motor and transmitter stators, so thatthe transmitter T-S transmits the angle of rotation of its stator about the xed rotor to a repeater R-i suitably mounted in fixed position on the craft.

The repeater R-li is similar to the repeater l't-l of Figs. 1 and 10, and controls the operation of the follow-up motor S-S in the same manner as repeater R-l controls the operation of servomotor S4. The motor S-l is suitably connected to the shaft 31' to operate the rudder and indicator control gearing in the manner illustrated in Figs. 1, 2. and 3.

The necessity for the use of the clutch mechanism in the apparatus illustrated in Fig. 1 3 will become apparent from consideration of Fig. 14. Let it be assumed that the craft V starts from the position J (Fig. 14) toward the transmitter X on the course L, with the fore-and-aft axis of the craft and pointers 28, 55 and I|1 all lined up `on saidcourse. In the absence of side winds, these indicator conditions would obtain until the craft arrived at the transmitter X.

Let it -be assumed that the craft is located at some position J-l 'laterally displaced from the course L through vthe transmitter X, that the receiver R-l of the radio compass is tuned to the frequency of the transmitter X, and that the directional gyro has been set forsome desired com- NOX. ,'I'hen, as the craft approaches the course L, the angle NOX decreases until it nally vanishes when the craft arrives at the course and thelines NO and OX coincide; that is, when the Eyro indicator alines with the line 28 on the dial 21 and the indicator $5 alines with the lubberline 56. These conditions obtain when the craft arrives at the position J-2 on the set compass course and is crabbing along the course toward drift automatically ccrthe transmitter X with rected.

Under the conditions just described, it is evident that 4the dial 21 and transmitter T75 must have been rotated counterclockwise through the angle NOX from the compass course defined by the gyro indicator ||1. Since the rotor shaft |22 of the transmitter is held stationary by the gyro a clockwise rotation of the fixed rotor shaft |22 shift theclutch mechanism of Figs. 3 and 13 toy cause engagement of the gears 39 and 5| with the gears 40 and 62, respectively, in order to steerthe This causes B' craft from-the position J-l on to the course L towardthe transmitter X If the craft be located in the position J-B and in movement away from the transmitter X, it is evident that the tuning of the receiver R-i to the frequency of the transmitter X will cause clockwise rotation of the indicator 28 through the angle ROX relative to the setting of the gyro indicatorv l I1. Tracing this rotation through the same elements to the shaft 31'. we nd the shaft 31 now` rotating clockwise through the angle ROX. The position of the gearing shown in Fig. 13 on shaft 31' is therefore correct for rotating the rudder I1 through an .angle proportional to the angle ROX to steer the craft on to the coursev L and away from the transmitter X.

- axis on said craftand settable to point in a fixed As the craft recedes from the transmitter X n with its rudder set clockwise in proportion to the angie ROX, this angle becomes smaller and y smaller until it finally vanishes when the craft arrives at the course L and the lines RO and OX coincide; that is, when the gyro .indicator ll1 alines with the line 2l on dial v21 and the indicator 65 alines with'the lubber-line 58. Whether the steering be effected manually or automatically, the rudder 41 will aline with the foreand aft axis of the craft, the pointer I5 will aline with the lubber-line 66. with the craft crabbing along the course L away from the transmitter X with drift automatically corrected.

Obviously, another automatic radio compass could be used with the .apparatus of Fig. 13 to train on a transmitter located to one side of the compass course set up on the directional gyroscope and to operate ground speed and position indicating mechanism in the manner shown in Figs. 1, 7, 8, 9 and 10. It is not believed necessary to illustrate this arrangement in detail,'since the necessary gearing and transmitter T would be identical with that employed to connect the compass 69 of Fig. 2 to the indicator mechanism operated by compasses I and 2.

While it` is preferable to use a separate wire for the sense antenna in each self-orienting radio v compass, the same effect may be secured by using the vertical effect of the directional antenna in the manner described on pages 96 to 98 of the third edition of Wireless Direction Finding, by R. Keen, published by Ilii'fe '8i Sons Ltd. of London. England; or described in Research Paper RP62l--pages 734' to 141 of Bureau of Standards Journal of Research, vol. 1l, December 1933.

The grooved pulley and cable connections between the follow-up motor of each radio cornv pass and the shaft for the loop antenna may be replaced by any suitable mechanical, electrical, pneumatic or hydraulic transmission; and, the mechanical relaysl for the motors S-4, S- and S-G may be replaced by the more efficient electronic relays such as are described in U. S. 'Patents 1,999,645 and 1,999,646, of April 30, 1935, or as are in common usein these radio compasses. The gearing connecting the follow-up motors is shown ln the drawings as enlarged out of all reasv compass direction; and mechanism,1controlled by the relative rotations of said devices about their said normally vertical axes, for steering the craft in a direction to eect coincidence of the vertical out the craft on whichthe rst'named device is Y held trained -and in drift-corrected movement in a predetermined direction along the compass course passing through said object and determined by the compass setting. of the second named device. 4-

2. A dirigible craft; a radio transmitter without said craft; a radio receiver on said craft tuned to the frequency of said transmitter, and including a directional'antenna rotatable about a normally vertical axis on said craft and means connected to said antenna and controlled by the output of said receiver for holding the antenna trained on said transmitter; a directional gyro- 4'scope rotatable about a normally vertical axis on said craft and settable to point in any desired compass direction; and means, controlled by the relative rotations of said antenna and gyroscope about their normally vertical axes, for steering s the craft on to and in drift-corrected movement in al predetermined direction along a compass course passing through said transmitter and determined by the setting of said directional gyroscope.

3. A- dirigible craft; steering means for said craft; two radio transmitters of different fre.- quencies spaced apart toldene for said craft a course lying in a vertical plane passing through said transmitters; two radio receivers mounted on Vsaid craft and adapted to be tuned to the frequency of either transmitter but each tuned to the frequency of a different transmitter, each receiver including a directional antenna rotatable about a normally vertical axis; a reversible motor connected to. and controlled only by the output of, one of said receivers; means connecting said motor to the directional antenna of said receiver to turn and hold the same trained on the transmitter to which said receiver is tuned; a reversible motor connected to, and controlled only by the output of, the other receiver; means connecting the last named motor to the directional antenna of that other receiver to hold thatlast named antenna trained on the other transmitter; and mechanism, including differential gearing, connecting said motors to said steering means to steer the craft on to and in drift-corrected movement along said course in a direction determined by the transmitter frequencies to which the respective receivers are tuned.

4. The apparatus set forth in claim 3 in combination with a pilot director having two indicaters rotatable on said craft; means connecting one of said indicators to one of said motors to rotate that indicator in synchronism with the directional antenna connected to said motor; and means connecting the other indicator to vthe other motor to rotate that other indicator in synchronism with the other directional antenna; said indicators being mounted to aline with each other only when the craft is located on said course.

5. The apparatus .set forth in claim 3 in combination with a steering indicator having a xed lubber-line and a pointer movable toward and.

to the frequenciesrrof any of said transmitters butY each tuned to the frequency of a different trans' mitter, each receiver including a'directional antenna rotatable about a normally vertical axis;

a reversible motor connectedv to, and controlled by the output of, one of said receivers, means connecting said motor to the directional antenna of that receiver to turn and hold said antenna trained on the transmitter to which its receiver is tuned; a reversible motor connected to, and

controlled by the output of another of, said three receivers; means connecting the second named motor to the directional antenna of that other receiver to turn and hold the same trained on the transmitter to which that other receiver is tuned; means including differential gearing connecting said motors to said steering mechanism to steer the craft on to and in drift-corrected movement along a straight course passing through thektwo transmitters'on which the two directional antennas are held trained by said motors and in a direction along said coursev determined by the transmitter frequencies to which the respective receivers are tuned; a third reversible motor connected to, and controlled by the output -of thev remaining receiver; means connecting the last named motor to the directional antenna of that remaining receiver to turn and hold the same trained on the remaining transmitter; a pilot director fixed to said craft and having three in dicators rotatable about a common axis thereon; and separate means connecting each of said motors individually to a separate one of said indicators to rotate each indicator in synchronism with the directional antenna to which its connected motor is also connected; said indicators and ldistances from each other, to` form a triangle,

of saidv objects, and for continuously indicating the position of the craft on said course.

9. The apparatus set forth in claim 8 in com' bination with mechanism controlled by said means for indicating the ground speed ofthe craft at the position indicated.

i. l0. The apparatus set forth in claim 8 in combination with mechanism controlled by said means forindicating the distance traversed by said craft along said course from any selected point on said course. s

11. A dirigible, craft; three direction determining`devices, each rotatable about a normally vertical axis on said craft; and means, controlled by holding said devices trained separately on three objects spaced apart without the craft at known distances from each other to forma triangle, for steering the craft on to and in driftcorrected movement in a predetermined direction along a straight course passing through any selected two yof said objects, and for continuously indicating the position of the craft on that course and the angle of drift of the craft at the position indicated.

12. A dirigible craft having a ,rudder normally alined with the fore-and-aft axis; mechanism for operating said rudder; two radio transmitters ofl different frequencies spaced apart to define a course; two radio receivers on said craft adapted ceiver; means connecting the second named motor to the directional antenna of that other receiver to turn and hold that last named antenna trained on the other transmitter; and means indirectional antennas being arranged to be maintained constantly by said motors in the same angular relation to each other as the angular relation between the vertical planes passing through said craft and the vthree radio transmitters. i

7. The apparatus defined by claim 6 in which said pilot director comprises: a dial controlled by one -of the two first named motors to rotate i on said craft and having an indicator extending across a diameter ofthe dial, a second indicator the common axis o f the other two indicators, said dial being provided with a scale cooperating with the third indicator to indicate the position of the craft on said course.

`8. A dirigible craft; three direction determining devices, each rotatable about a normally verti` cal axis on said craft; and means, controlled by holding said devices trained separately on three objects spaced apart without the craft at known cluding differential gearing connecting said motors to said mechanism to turn the rudder, vresponsive to off-course condition of the craft, in the direction required to steer the craft on to and in drift-corrected-movement in a predetermined direction along said course, and to maintain the rudder inclined to saidfore-and-aft axis at an angle proportional to the difference between the -exterior and interior opposite angles at the base of the triangle formed with said course by straight lines drawn to the craft from said transmitters 'alined with the fore--and-aft axis; mechanism for operating said rudder; two radio transmitters of different frequencies spaced apart to define a course; two radio receivers on said craft adapted to be tuned to the frequency of either transmitter but tuned to the vfrequency of a different one of said transmitters, each receiver including a directional antenna rotatable about a normally asesinas vertical axis; a-reversible motor connected to, and controlled by the output of, one of said receivers; means connecting'said motor to the directional antenna of said receiver to turn and hold the same trained on the transmitter to which its receiver is tuned; a reversible motor connected to, and controlled by, the output of the other receiver; means connecting the second named motor to the directional antenna of that other receiver to turn and hold the same trained on the other transmitter; and means including differential gearing connecting said motors to lsaidmechanism to turn the rudder, responsive to "off course condition of the craft, in the direction required to steer the craft on to and in driftcorrected movement in a predetermined direction along said course, and to maintain the rudder inclined to said fore-and-aft axis at an angle proportional to the sum of the angles at the base oi' the triangle formed with said course by straight lines drawn to the craft from said transmitters when the craft is located in the zone lying` between said transmitters and bounded by vertical planes perpendicular to said course and passing through said transmitters, the direction of move- 4ment of the craft along said course being determined by the transmitter frequencies to which the respective receivers are tuned.

14. A dirigible craft; steering means for said craft; two direction determining devices, each rotatable about a normally vertical axis on said craft; mechanism controlled by the rotation of said devices about said axes for operating said steering means; a pilot director including two sitions defining thecourse for the craft.

115. A dirigible craft; steering means for said craft; two direction determining devices, each rotatable about a normally vertical axis on said craft; mechanism controlled by the rotation of said devices about said axes for operating said steering means: a pilot director including two indicators rotatable about a common axis on said craft; means for transmitting the rotation of one of said devices to one of said indicators; means for transmitting the rotation of the other device to the other indicator, said indicators being mounted on said craft to aline substantially with each other'upon rotation of said devices about 16. A dirigible craft: steering means for said craft: two direction determining devices, each roy tatable about a normally vertical axis on said craft; mechanism connected to, and controlled only by the rotation of said devices about said axes for operating said steering means; a steering indicator having a fixed lubber-line and a pointedmovable toward and from said lubberline; and means connecting said pointer to said mechanism to cause said pointer to register with said lubber-line upon rotation of said devices about their said vertical axes to predetermined relative positions defining the course for the craft.

17. A dirigible craft; two direction determining devices, each mounted to rotate freely about a normally vertical axis on said craft and to be trained independently in all directions in azimuth; and mechanism connected to, and controlled by the relative rotations of, said devices only about their said vertical axes for steering the craft in directions to cause the direction lines of saidA devices to move into, and be maintained in, a vertical plane passing through any two objects spaced apart to dene a course for said craft and upon which said devices are separately held trained.

18. The herein described method of automatically steering a dirigible craft from any location on to and along a straight course passing in a predetermined compass direction through a source of radiant energy, which comprises: visually setablishing on said craft the desired line of compass direction; receiving energy from said source; 4 continuously and visually establishing from said received energy and independently of the compass heading ofsaid craft the line of direction from the craft to said source; and controlling in accordance with the such received energy automatically the l`steering of the craft to effect and maintain substantialdcoincidence between said lines.

19. The herein described method of automatically steering a dirigible craft from any location on to and along a straight course passing in a predetermined compass direction through a source of radiant energy, which comprises: visually establishing onsaid craft the desired line their'said vertical axes to predetermined relative positions defining the course for the craft.

of compass direction; receiving energy from said source; continuously and visually establishing from said received energy and independently of the compass heading of said craft the line of direction lfrom the craft to said source.; measuring the angle between said lines of direction; and controlling in accordance with such measurement automatically the steering of the craft from any location on to and along said course.

- JOSEPH DUGAN. 

